Methods and systems for removing polar compounds from a metal-containing solution

ABSTRACT

Methods and systems for removing polar compounds from a metal-containing solution. According to various example aspects, methods and systems for removing hydrolysis byproducts and other polar compounds from a metal-loaded organic solution of a solvent extraction process.

FIELD

The disclosure relates to methods and systems for removing polar compounds from a metal-containing solution. In certain example aspects, the disclosure relates to removing hydrolysis byproducts and other polar compounds from a metal-loaded organic solution of a solvent extraction process.

BACKGROUND

Metals are commonly procured by a leaching process (e.g., heap/dump leaching, vat leaching, agitation leaching, bioleaching, autoclave leaching, etc.) in combination with solvent extraction, stripping and electrowinning processes. In a leaching process, sulfuric acid or an ammoniacal leaching solution, for example, can be applied to an ore or scrap pile such that the metal (e.g., copper and copper alloys) is dissolved into the aqueous leaching solution. The resulting metal-bearing aqueous solution (a.k.a. “pregnant leach solution” or “PLS”) is transferred to a solvent extraction plant, where it undergoes mass transfer of the metal from the PLS to an organic solution via contact of the two solutions under vigorous mixing.

In the solvent extraction process, the organic solution typically contains an extractant dissolved in a kerosene-like hydrocarbon diluent. The metal (e.g., copper as cupric ion) can form a chelate-type complex with the extractant. The metal transfers from the aqueous solution into the organic solution as an ion, and subsequently, the metal-depleted aqueous solution and the metal-loaded organic solution are separated. The metal-depleted aqueous solution exits the solvent extraction process as raffinate, and the metal-loaded organic solution proceeds to a stripping process, where it undergoes a mass transfer of the metal to an electrolyte aqueous strip solution. During stripping, the metal is transferred to an electrolyte aqueous solution and protons are transferred to the organic solution. The resulting metal-depleted organic solution returns to the solvent extraction process for re-use whereas the metal-rich aqueous strip solution is transferred to an electrowinning process. During electrowinning, the metal is electro-deposited from the metal-rich aqueous strip solution to make, for example, 99.99% pure elemental copper, which can be directly turned into commercial rod or wire at a furnace operation without further refining. Notably, in a typical leaching process, the temperature of the PLS can range from about 10° C. to about 30° C. Consequently, the temperatures during solvent extraction typically range from about 20° C. to about 25° C., and the temperatures during stripping can range from about 30° C. to about 35° C. The temperature in the electrowinning cells is typically about 45° C.

Problems arise in a solvent extraction process when the extractant or other compounds degrade via chemical hydrolysis of an organic component. The rate of hydrolysis can depend on a variety of operational factors including the organic acid concentration, the concentration of contaminants, the temperature of the PLS feed and strip solutions, and the presence of impurities in the PLS and/or the organic phase, all of which can promote hydrolysis. Depending on the operational parameters of the overall solvent extraction process, hydrolysis byproducts can build up in the organic solution until the rate of formation equals the rate of loss in entrainment. Due to their polar nature, the hydrolysis byproducts can increase the surface activity of the organic phase resulting in operational problems such as increased phase disengagement times and increased crud formation. As the concentration of the hydrolysis byproducts increases, the byproducts contribute to an increase in the viscosity and density of the organic solution resulting in increased operating problems with aqueous carryover from extraction to stripping due to aqueous entrainment in the loaded organic as well as losses of expensive organic phase due to entrainment in the aqueous raffinate exiting the extraction process. Increased aqueous entrainment results in carryover of undesirable metals to the metal recovery process which causes contamination or additional operating problems. Because density and viscosity of the organic phase increases with an increase in the extractant concentration, the problems due to increased hydrolysis can be more significant for plants operating at higher reagent concentrations.

One trend in the industry is to treat copper sulfide concentrates via hydrometallurgical processes rather than by smelting processes. Such hydrometallurgical processes produce high temperature and/or high acid concentration leach solutions. Separately, other processes located upstream of the solvent extraction process can also detrimentally affect the temperature, viscosity, density, surface activity, etc. of the PLS, resulting in an increase in hydrolysis of organic components. For example, in a hydrometallurgical process, the PLS entering the solvent extraction process can range in temperature from about 35° C. to 50° C., or even higher, as compared to 10° C. to 30° C. for a standard PLS solution. Higher temperatures can also occur when the oxide ores are extremely rich in the metal minerals, as with the ores from the Democratic Republic of the Congo. Such ores are typically vat or agitation leached with sulfuric acid, and they have more reactive mass per unit volume such that the exothermic nature of the leaching reactions is more noticeable. Furthermore, climate conditions at the leaching site, the size of the raw ore or metal, and the drip irrigation rate can all affect the temperature of the PLS that enters the solvent extraction plant.

The amount of organic component hydrolysis can approach a level of at least 100% of the extractant concentration in the organic solution. Such degradation can cause a significant increase in the viscosity and density of the organic solution, which in turn causes slower phase disengagement and higher entrainments. Moreover, the buildup of hydrolysis byproducts can result in degradation “run-away”, which can lead to massive organic solution losses, loss of metal production, and plant shutdowns.

There is a need for methods and systems for removing hydrolysis byproducts and other polar compounds from a metal-containing solution, for example, a metal-loaded organic solution of a solvent extraction process.

SUMMARY

According to various example aspects, the disclosure relates to a method for removing polar compounds from a solution, comprising: contacting an organic solution comprising non-polar metal complexes and polar compounds with a polar solid and adsorbing the polar compounds onto the polar solid.

The method can further include contacting the organic solution with a clay prior to contacting the organic solution with the polar solid. The clay can be a material such as montmorillonite, smectite, heulandite, mordenite and combinations thereof. The clay can be comprised in a tank, bed or column. In certain example aspects, the clay removes aqueous components from the organic solution to a concentration of about 3000 ppm or less of the aqueous components.

The method can further include settling the organic solution in a tank until an organic phase separates from an aqueous phase; and removing the aqueous phase and/or coalescing the organic solution with a coalescer or an electrostatic coalescer to separate an organic phase from an aqueous phase; and removing the aqueous phase.

The polar solid can be comprised in a low-pressure column or a pressure column. The organic solution can be partially loaded with the non-polar complexes or the organic solution can be fully loaded with the non-polar complexes. The organic solution can include a water immiscible solvent and a reagent such as a ketoxime, an aldoxime or combinations thereof. The water immiscible solvent can be kerosene, benzene, toluene, xylene or combinations thereof. The organic solution can include a phenolic oxime. The concentration of the phenolic oxime in the organic solution can be about 0.018 M to about 1.1 M. The phenolic oxime can be a ketoxime or an aldoxime at a concentration of about 0.018 M to about 0.9 M. The phenolic oxime can be modified or non-modified. The organic solution can include 3-methyl ketoxime, 3-methyl aldoxime, 2-hydroxy-5-nonylacetophenone, 5-nonylsalicylaldoxime, 5-dodecylsalicylaldoxime, or combinations thereof. The organic solution can include a 3-methyl ketoxime and a 3-methyl aldoxime in a molar ratio of about 85:15 to about 25:75.

The non-polar complexes can include a metal such as copper, iron, nickel, zinc, metal alloys thereof or combinations thereof. The polar compounds can include phenolic oxime compounds and oxime hydrolysis byproducts. The oxime hydrolysis byproducts can include ketone compounds, aldehyde compounds or combinations thereof.

The method can include receiving the organic solution from a solvent extraction process. The polar solid can include silica, alumina, activated carbon or combinations thereof. The method can include regenerating the polar solid to remove adsorbed polar compounds by contacting the polar solid with a polar solvent.

In various example aspects, the disclosure relates to a method of recovering metal from a metal-containing aqueous solution, comprising: contacting an aqueous solution comprising a metal with an organic solution to extract a portion of the metal into the organic solution and forming a metal-loaded organic solution comprising polar compounds and a metal-depleted aqueous solution; separating the metal-loaded organic solution from the metal-depleted aqueous solution; removing a portion of the polar compounds from the metal-loaded organic solution by contacting the metal-loaded organic solution with a polar solid to adsorb the polar compounds onto the polar solid and forming a treated metal organic solution; recovering metal values from the treated metal organic solution.

The method can include contacting the metal-loaded organic solution with a clay prior to the contacting with the polar solid. The clay can include montmorillonite, smectite, heulandite, mordenite or combinations thereof. The clay can be comprised in a tank, bed or column. The clay can remove aqueous components from the organic solution to a concentration of about 3000 ppm or less of the aqueous components.

The method can further include receiving the aqueous solution from a process selected from a group consisting of heap leaching, hydrometallurgical leaching, high pressure leaching, oxidative leaching, biologically assisted leaching and combinations thereof. The aqueous solution can be at a temperature of about 20° C. to about 60° C. The metal values can include copper, iron, nickel, zinc, metal alloys thereof or combinations thereof.

The organic solution can include a water immiscible solvent and a reagent selected from a group consisting of a ketoxime, an aldoxime and combinations thereof. The organic solution can include a water immiscible solvent and a reagent such as a ketoxime, an aldoxime or combinations thereof. The water immiscible solvent can be kerosene, benzene, toluene, xylene and combinations thereof. The organic solution can include a phenolic oxime. The concentration of the phenolic oxime in the organic solution can be about 0.018 M to about 1.1 M. The phenolic oxime can be a ketoxime or an aldoxime at a concentration of about 0.018 M to about 0.9 M. The phenolic oxime can be modified or non-modified. The organic solution can include 3-methyl ketoxime, 3-methyl aldoxime, 2-hydroxy-5-nonylacetophenone, 5-nonylsalicylaldoxime, 5-dodecylsalicylaldoxime, or combinations thereof. The organic solution can include a 3-methyl ketoxime and a 3-methyl aldoxime in a molar ratio of about 85:15 to about 25:75.

The polar compounds can include phenolic oximes and oxime hydrolysis byproducts. The oxime hydrolysis byproducts can include ketone compounds, aldehyde compounds or combinations thereof.

The step of contacting the aqueous solution with the organic solution and separating the metal-loaded organic solution from the metal-depleted aqueous solution can be via a solvent extraction process. The step of removing a portion of the polar compounds from the metal-loaded organic solution comprises, passing a bleed stream from a main stream of the metal-loaded organic solution through the polar solid and passing the treated metal organic solution to the main stream.

The method can further include measuring one or more parameter of the metal-loaded organic solution and of the treated metal organic solution and adjusting a flow rate through the polar solid based on the measured parameter. The one or more parameter is indicative of an amount of polar compounds in the metal-loaded organic solution and the treated metal organic solution. The one or more parameter can be conductivity, viscosity, density, pH, temperature, pressure and combinations thereof. Adjusting the flow rate based on the one or more parameter can include adjusting the flow rate to achieve at least one of a target conductivity and target viscosity of the treated metal organic solution. The method can include measuring the one or more parameter of the aqueous solution.

The polar solid can be comprised in a low-pressure column or a pressure column. The polar solid can include a material such as silica, alumina, activated carbon or combinations thereof. The method can further include regenerating the polar solid to remove adsorbed polar compounds by contacting the polar solid with a polar solvent.

The above summary provides a basic understanding of the disclosure. This summary is not an extensive overview of all contemplated aspects, and is not intended to identify all key or critical elements or to delineate the scope of any or all aspects of the disclosure. Its sole purpose is to present one or more aspects in a summary form as a prelude to the more detailed description that follows and the features described and particularly pointed out in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a system according to various example aspects of the disclosure.

FIG. 2 shows a system according to various example aspects of the disclosure.

FIG. 3 shows a system according to various example aspects of the disclosure.

FIGS. 4.1 and 4.2 show results of Example 1, hydrolysis products removed vs. amount of silica gel and oxime removed.

FIGS. 5.1 and 5.1 show results of Example 2, hydrolysis products removed vs. contacts with silica gel and oxime removed.

FIGS. 6.1, 6.2 and 6.3 show results of Example 4, silica gel re-use. HNA, NSA and NP bars are left to right.

FIG. 7.1 shows results of Example 5, silica gel loading capacity in a flash column. HNA, NSA, NP and CU bars are left to right.

FIG. 8.1 shows results of Example 6, silica gel large column comparison. Starting Organic, 40 g Silica Column and 4^(th) Pass (40 g total) bars are left to right.

FIGS. 9.1, 9.2 and 9.3 show results of Example 7, alumina use as a polar solid. Starting Organic, Activated Alumina Organic, Basic Alumina Organic and Silica Organic bars are left to right in FIG. 9.1. Activated Alumina, Basic Alumina and Silica bars are left to right in FIGS. 9.2 and 9.3

DETAILED DESCRIPTION

Example aspects are described herein in the context of methods and systems for removing polar compounds from a metal-containing solution. Those of ordinary skill in the art will recognize that the following description is illustrative only and is not intended to be in any way limiting. Other aspects will readily suggest themselves to those of ordinary skill in the art having the benefit of this disclosure. Reference will now be made in detail to implementations of the example aspects as illustrated in the accompanying drawings. The same reference indicators will be used to the extent possible throughout the drawings and the following description to refer to the same or like items.

FIG. 1 shows an example of polar compounds removal system according to various example aspects of the disclosure. A stream (e.g., the total stream, a bleed stream, or a bypass) of a metal-loaded organic solution can flow into polar compounds removal column via an optional drying vessel. The system of FIG. 1 can operate as a batch, semi-continuous or continuous process as would be understood by those of ordinary skill in the art. The metal-loaded organic solution can be from a solvent extraction process (not shown) or any other process that produces a metal-loaded organic solution stream. In certain aspects, the metal in the metal-loaded organic solution stream is a valuable metal including, but not limited to, copper, iron, nickel, zinc, metal alloys thereof and combinations thereof. The organic solution can be any suitable solution for absorbing the metal from an aqueous solution (e.g., a pregnant leach solution or “PLS”) and contains an extracting reagent (or extractant).

The metal-loaded organic solution is at least partially loaded with the non-polar metal complexes. According to various example aspects of the disclosure, the metal-loaded organic solution is at least 80% of its maximum loading capacity, or at least 90% of its maximum loading capacity, or at least 95 to about 100% of its maximum loading capacity. A fully metal-loaded organic solution is at about 100% of capacity such that there is no free phenolic oxime capacity remaining. Depending on the operating parameters of the solvent extraction plant, it may be necessary to increase the metal loading of the organic solution. This can be carried out by contacting the metal-loaded organic solution with fresh volumes of PLS feed, which can require about one (1) to about four (4) additional contacts with PLS feed solution to achieve about 95 to about 100% of maximum loading.

In certain example aspects, the extracting reagent is an oxime, such as a phenolic oxime, which is dissolved in a water immiscible solvent including, but not limited to, kerosene, benzene, toluene, xylene and combinations thereof to form the organic solution. Phenolic oximes can be phenolic ketoximes and phenolic aldoximes and can be non-modified or modified. In certain example aspects, the organic solution can include a mixture of one or more ketoximes with one or more aldoximes at a molar ratio of about 10:90 to about 90:10 of the ketoximes to the aldoximes. For example, the organic solution can include 3-methyl ketoxime and a 3-methyl aldoxime in a molar ratio of about 85:15 to about 25:75. Non-modified phenolic oximes include ketoxime- or aldoxime-based reagents in a hydrocarbon diluent such as LIX 84-I (2-hydroxy-5-nonylacetophenone oxime in a hydrocarbon diluent), LIX 860N-I (5-nonylsalicylaldoxime in a hydrocarbon diluent) or LIX 860-I (5-dodecylsalicylaldoxime in a hydrocarbon diluent). Non-modified reagents also include mixtures of a ketoxime with an aldoxime in varying proportions such as LIX 984N (50:50 v/v LIX 84-I and LIX 860N-I), LIX 973N (30:70 LIX 84-I and LIX 860N-I). Modified reagents include a thermodynamic modifier in the formulation to improve metal (e.g., copper) stripping. Modified reagents are typically a mixture of an aldoxime such as the 5-nonylsalicylaldoxime with a thermodynamic modifier. Examples of thermodynamic modifiers include, but are not limited to, highly branched chain aliphatic or aliphatic-aromatic C₁₀ to C₃₀ esters or C₁₄ to C₃₀ alcohols, α-hydroxy oximes (e.g., 5,8-diethyl-7-hydroxy dodecane-6-oxime or a mixture of 1-(4′-alkylphenyl)-1,2-propanedione dioximes), 2,2,4-trimethyl-1,3-pentanediol mono-isobutyrate, 2,2,4-trimethyl-1,3-pentanediol mono-benzoate, 2,2,4-trimethyl-1,3-pentanediol di-isobutyrate, 2,2,4-trimethyl-1,3-pentanediol di-benzoate, isobutyl heptyl ketone, nonanone, 2,6,8-trimethyl-4-nonanone, diundecyl ketone, 5,8-diethyldodecane-6,7-dione, and tridecanol. The phenolic oxime in the organic solution can be at a concentration of about 0.018 M to about 1.1 M.

Absorption of the metal from the aqueous solution into the organic solution results in the formation of a non-polar chelate-type metal complex with the extractant. Polar compounds (e.g., hydrolysis byproducts) can also form as a result of various operational factors in the solvent extraction process including the organic acid concentration, the concentration of contaminants, the temperature of the PLS feed and strip solutions, and the presence of impurities in the PLS and/or the organic phase. Additionally, any metal-free extractant, that is, excess extractant that did not form a complex with the metal, can also be polar. As such, the metal-loaded organic solution can contain non-polar complexes as well as polar compounds. The concentration of total active phenolic oxime extractants (i.e., free oximes plus oximes incorporated into the metal complex) plus hydrolysis byproducts can range from about 0.075 M to about 1.3 M, or from about 0.15 M to about 1.3 M, or from about 0.22 M to about 1.0 M, or from about 0.22 M to about 0.9 M in the organic solution. Removal of the polar compounds from the organic solution can prevent, among other things, buildup of hydrolysis byproducts, increases in viscosity and density of the organic solution and “run-away” degradation of the extractant.

As shown in FIG. 1, the system includes a polar compounds removal column for removing polar compounds, such as hydrolysis byproducts (e.g., ketones, aldehydes), and other polar compounds (e.g., metal-free oximes, humic acids derived from the leach, chemicals such as flocculants, leaching aids, filter aids used in producing the PLS and contaminants such as cleaning detergents and lubricating oils) from the metal-loaded organic solution. The column includes a polar solids material capable of adsorbing the polar compounds from the metal-loaded organic solution. The polar solids material can include, but is not limited to, silica, alumina, activated carbon or combinations thereof. In certain example aspects, the polar solids material is activated silica or activated alumina or a combination thereof. The polar solids material should be selected based on its ability to adsorb the particular polar compounds in the metal-loaded organic solution, its compatibility with the metal-loaded organic solution (e.g., pH, chemical reactivity, etc.) and its coarseness to enable high flow rates.

According to certain example aspects, the polar solids material can be activated silica, silica gel, silica beads, silica powder, silica slurry (e.g., silica powder suspended in hexane or other organic solvent) and combinations thereof. For industrial applications, the silica polar solids material can be a coarse silica, which may be relatively inexpensive as compared to other types of silica materials (e.g., silica gel) and which would enable high flow rates through the silica polar solids material in the column.

The polar compounds removal column can be any suitable device for enabling the metal-loaded organic solution (or optionally the dried metal-loaded organic solution) to come into sufficient contact with the polar solids material. In certain example aspects, the polar compounds removal column is a low-pressure column operating at about 2 atm or less, a pressure column operating at above 2 atm, a flash column or a packed column. The polar compounds removal column could also be one or more stirred tanks where the polar solids material is mixed with the metal-loaded organic solution and then the polar solids material, hydrolysis byproducts and other polar compounds are separated from the organic phase by filtration, decantation or any other process suitable for separating such components as known to those of ordinary skill in the art. Any combination of columns, stirred tanks, pumps and filters can be used to facilitate flow of the metal-loaded organic solution through the polar compounds removal circuit.

In addition to polar and non-polar compounds, the metal-loaded organic solution can also contain small amounts of entrained aqueous. Removing the aqueous with an optional drying vessel as shown in FIG. 1 can enhance the polar components removal operation. In certain example aspects, the drying vessel can remove aqueous from the metal-loaded organic solution to a concentration of about 3000 ppm or less of water, or about 1000 ppm or less of water, or about 300 ppm or less of water, or about 100 ppm or less of water, or about 50 ppm or less of water. The drying vessel can be any suitable open or closed batch or semi-continuous tank that includes a material for removing (e.g., drying) aqueous components from the metal-loaded organic solution. In certain example aspects, the drying vessel can be a stirred tank constructed of, for example, stainless steel or a fiber reinforced plastic.

The material within the optional drying vessel for removing aqueous components can include, but is not limited to, activated clay in an amount of about 0.5% wt/vol to about 10% wt/vol, or about 1% wt/vol to about 4% wt/vol. Any clay used in the chemical industry for decolorization of vegetable or mineral oils can be used. The clay can be a montmorillonite or smectite clay. According to certain example aspects, the clay can be an acid-activated montmorillonite clay such as, a Super Filtrol Grade 1 acid treated clay, Filtrol Grade 25 acid treated clay, Engelhard F20 clay, a heulandite clay, a mordenite clay and combinations thereof. The clay material can have a layered silicate structure. Montmorillonite and smectite clays carry negative surface charges (e.g., SiO₄ tetrahedra with lattice substitution) balanced by interlayer cations (e.g., Ca²⁺). The interlayer spacing can be about 10 Å to about 15.5 Å. The interlayer spaces of these clays can be penetrated by cations, water and layers of polar organic liquids. Acid activation of the clay leaches out certain elements in the clay lattice, creating a large surface area of about 250 m²/g.

According to various example aspects of the disclosure, other methods (besides or in addition to clay treatment) for removing aqueous components from the metal-loaded organic solution are contemplated. Examples include 1) allowing the metal-loaded organic solution to stand in a tank for a period of time so that the aqueous phase can separate from the organic phase, and 2) passing the organic solution through a coalescer or an electrostatic coalescer. Examples of suitable coalescers are described in U.S. Pat. Nos. 6,413,429 and 5,772,730 and examples of electrostatic coalescers are described in U.S. Pat. Nos. 3,616,460, 8,702,952 and 9,039,884.

In certain example aspects, the system of FIG. 1 can optionally include two or more drying vessels such that one can maintain operation while the other vessels are serviced. The material within the drying vessel can be replaced or regenerated from time to time as it begins to lose efficacy for removing aqueous components. Similarly, the system of FIG. 1 can optionally include two or more polar components removal columns so that while one is in operation, the other(s) can be serviced or regenerated. During servicing or regeneration, the spent adsorbent in the polar components removal column(s) can be stripped of the hydrolysis byproducts by passing a polar organic solvent through the column and/or washing the recovered solids. The cleaned column and adsorbent is then ready for use. A variety of instruments can be used to monitor the organic solution exiting the polar components removal vessel to determine if servicing or regeneration is required. For example, gas chromatography, thin layer chromatography, liquid chromatography and infrared spectroscopy can be used to monitor the organic solution exiting the polar components removal column for breakthrough of polar compounds.

During operation (in reference to FIG. 1), the metal-loaded organic solution flows through a main line to, for example, a stripping and/or electrowinning process. A bleed line can be used to divert a portion of the main line through the polar compounds removal system. In certain example aspects, the entire main line (not just a bleed line) can be directed through the polar compounds removal system (not shown). In the bleed line, the metal-loaded organic solution can flow into an optional drying tank to remove water from (or dry) the metal-loaded organic solution. Removing the aqueous components from the metal-loaded organic solution can be desirable, particularly if such components have a tendency to degrade and/or affect the performance of the polar solids material in the polar compounds removal column. The metal-loaded organic solution (or optionally the dried metal-loaded organic solution) flows into the polar compounds removal column where the polar compounds are adsorbed onto the polar solids material.

The treated metal-loaded organic solution exiting the column is depleted in polar compounds. For example, the metal-loaded organic solution entering the bleed line can contain polar compounds at an amount that is about 50% to about 100% higher than the amount of polar compounds in the treated metal organic solution exiting the polar compounds removal column. As will be described in further detail below, a control system can be used to achieve a target polar compounds concentration in the treated metal organic solution. The treated metal organic solution is then returned to the solvent extraction circuit.

In the optional drying vessel, the drying material (e.g., clay) can be mixed with the metal-loaded organic solution and then agitated for a period of time (e.g., about 1 min to about 24 hours, or about 1 min to about 12 hours, or about 1 min to about 6 hours, or about 1 min to about 3 hours, or about 1 min to about 90 min, or about 1 min to about 45 min). For clay treatment, short contact times (e.g., about 3 hours or less, or about 1 hour or less, or about 30 min or less) can be important because the surfactants are captured very quickly by the clay, but over time the oximes begin to adsorb onto the clay and displace the surfactants lessening the effect of clay treatment. The clay can be subsequently separated from the dried metal-loaded organic solution by sedimentation or pressure filtration. For clay treatment using sedimentation to separate the clay from the organic solution, the mixer can be turned off after about 5 minutes. Thereafter, the clay is allowed to settle and the dried organic solution is decanted out of the vessel. Finally, the wetted clay is drained out of the vessel. For clay treatment using a pressure filter, the organic solution can be mixed for the entire filtration cycle of about 30 minutes to about 60 minutes in order to provide a mixed feed for the filter. According to various example aspects, the phase disengagement and extraction kinetics of the organic solution before and after clay treatment can be measured.

FIG. 2 shows a system according to various example aspects of the disclosure. The system of FIG. 2 can include ore leaching, solvent extraction, stripping and electrowinning operations together with a polar compounds removal system. The leaching operation can be of any type known to those of ordinary skill in the art including heap leaching, hydrometallurgical leaching, high pressure leaching, oxidative leaching, biologically assisted leaching and combinations thereof. In certain aspects, the leaching operation results in an aqueous pregnant leaching solution having a temperature of about 20° C. to about 60° C., or about 25° C. to about 55° C., or about 35° C. to about 50° C. and/or having a pH of about 0 to about 7, or about 0 to about 6, or about 0 to about 5.

The solvent extraction operation can be any suitable system known to those of ordinary skill in the art. Similarly, the stripping and electrowinning operations can be any suitable operations known to those of ordinary skill in the art.

Successful solvent extraction/electrowinning (“SX/EW”) operations involve a delicate management of the solvent extraction plant and the organic solution stream within. A closed loop circuit can consist of extraction stages followed by stripping stages and, in some cases, secondary stages for washing and/or treating the organic solution. The extractant species in the organic solution is typically selected based on the metal or metals in the PLS and can consist of various compounds from tertiary-amines to hydroxyl-oximes. However, in the context of copper recovery, the extractant can be a phenolic-oxime. According to various example aspects of the disclosure, the system as shown in FIG. 2 can be used for a variety of valuable metals (discussed above), and below are general chemical structures of extractants for copper.

General Structure of Copper Extractants

Reagent R A LIX ®65 C₁₂H₂₅ C₆H₅ LIX ®65N C₉H₁₉ C₆H₅ SME 529 & LIX ®84-I C₉H₁₉ CH₃ P1 & LIX ®860N-I C₉H₁₉ H LIX ®860-I C₁₂H₂₅ H

The extraction and stripping equilibrium in copper solvent extraction is driven by copper concentration in extraction and acid concentration in stripping. For example, in extraction, the phenolic hydroxyl proton is donated to the aqueous phase and copper(II) ion binds, non-covalently, to the hydroxyl oxygen in a 2:1 stoichiometry (two extractant molecules to one copper(II)). In stripping, the copper ion is stripped off by re-protonation of the phenolic hydroxyl group by the high acid concentration in the strip electrolyte solution. Such reactions are listed below.

Cu++(aq)+2RH(org)→R₂Cu(org)+2H+(aq)  Extraction Reactions

-   -   where:     -   Cu++ (aq)—is copper in PLS solution     -   RH (org)—is the extractant i.e. stripped organic     -   R₂Cu (org)—is the copper/extractant complex i.e. loaded organic     -   2H+ (aq)—is acid in raffinate solution.

R₂Cu(org)+2H+(aq)→Ca++(aq)+2RH(org)  Stripping Reactions

-   -   R2Cu (org)—is the copper complex i.e. loaded organic     -   2H+ (aq)—is the acid in the spent electrolyte solution     -   Cu++ (aq)—is the copper in the advance electrolyte solution     -   2RH (org)—is the stripped copper complex.

A drawback in the implementation of heap-leaching/SX/EW is the low solubility of copper sulfide ores in acidic or basic aqueous solutions, making this technology historically applicable only to the harvesting of oxide ores. In recent years there have been significant improvements in technologies to improve solubility of copper sulfides in aqueous solutions. At Konkola Deeps in Zambia the copper sulfide ore was concentrated by flotation and sent to high-pressure acid leach. Avecia Notes, Hydrometallurgy, Proceedings of the International Symposium honoring Professor Ian M. Ritchie, p. 1429-1446 (August 2003, Minerals, Metals & Materials Society, Vancouver, B.C., Canada). In 2007, Phelps Dodge, now Freeport McMoRan Inc., demonstrated large-scale high-pressure oxidative leach to oxidize the sulfide ore. Marsden et al., Copper Concentrate Leaching Developments by Phelps Dodge Corporation, Phelps Dodge Corporation, Phoenix, Ariz., USA. (2007, Young, Courtney). These technologies, and many other similar technologies, have one overarching similarity: the generation of a high temperature, high acid concentration, and high copper concentration PLS solution. These solutions can be treated by SX/EW to produce high-grade elemental copper, with a major drawback: significantly increased degradation of the organic stream in the SX circuit.

The oxime functionality (—CR═N—OH) of the reactant undergoes acid catalyzed hydrolysis to produce the phenolic aldehyde/ketone (—CR═O). This is the primary route of chemical degradation of the active extraction reagent in copper SX operation. Historically, the contact of the organic stream with the stripping electrolyte was the main contributor to hydrolysis because of the temperature (about 30° C. to about 40° C.) and acid concentration (about 150 g/L to about 200 g/L H₂SO₄) in such electrolyte liquors. However, with the advent of high pressure leach, oxidative leach, biologically assisted leach, and other technologies to leach sulfide ores, the leach solution introduced into a copper SX plant can be an additional, if not major, contributor to hydrolysis in the copper SX circuit. Given the reciprocating loop design of SX plants, these hydrolysis products build up in the organic phase and have no extractive capacity. This is a major problem for these operations because this hydrolysis build up will increase the viscosity of the organic phase, which in turn leads to much higher entrainment losses and generation of solid-stabilized-emulsions (“CRUD”). Additionally, because these hydrolysis products are polar, they can act as a chemical modifier suppressing the extractive strength of the organic phase. Higher viscosity in the organic phase can also lead to entrainment of aqueous from both extraction and stripping solutions into the organic phase, which leads to even higher degradation rates. The sum of these complications generates a positive-feedback-loop to create an exponential “run-away” degradation rate, where a copper SX plant can turn over an entire inventory of extractant much faster than normal. Preventing run-away degradation involves reducing CRUD generation by reducing organic phase viscosity. Selective removal of hydrolysis byproducts from SX circuits can prevent such complications.

Selective removal of these hydrolysis byproducts in, for example, a copper SX operation can be accomplished by solid phase extraction using a polar stationary phase (i.e., a polar solids material). Notably, unbound (i.e., stripped of metal or metal-free) oxime is polar enough to bind to the polar solids material, while the metal (e.g., copper) complex (e.g., oxime2-Cu) is non-polar. As shown in FIG. 2, at least a portion of the metal-loaded organic solution can be diverted from the SX process and into a polar compounds removal system as described above with respect to FIG. 1.

During operation of the polar compounds removal system shown in FIG. 2, and as similarly described above with respect to FIG. 1, the metal-loaded organic solution can be optionally passed through a drying vessel and then through the polar components removal column leaving behind the polar compounds, including any unloaded oxime and any hydrolysis product. This polar solid bed can then be stripped with a polar solvent and the hydrolysis byproducts, plus any unloaded oxime bound to the polar solid, can be collected. This mixture can then be regenerated back into the oxime by distilling away the solvent used to strip off the hydrolysis byproducts followed by oximation, and then reintroduced into the SX plant as fresh oxime extraction reagent.

According to various example aspects of the disclosure, a control system can be used to control the removal rate of polar compounds from the system as shown in FIG. 3. A controller, for example, a programmable logic controller (“PLC”), can be connected to one or more sensors for measuring parameters of the fluid in the system and can also be connected to a device for controlling flow rate through the polar components removal system. The one or more sensors can measure conductivity, viscosity, density, pH, flow rate, temperature and any other parameter suitable for controlling the removal rate of polar compounds from the metal-loaded organic solution (or the dried metal-loaded organic solution). The device for controlling flow rate can be any suitable device known to those of ordinary skill in the art. For example, the device can be a positive displacement pump, a centrifugal pump, a peristaltic pump, a rotameter among others.

Following are some embodiments of the invention.

E1. A method for removing polar compounds from a solution, comprising contacting an organic solution comprising non-polar metal complexes and polar compounds with a polar solid and adsorbing the polar compounds onto the polar solid. E2. The method of embodiment 1, further comprising: contacting the organic solution with a clay prior to contacting the organic solution with the polar solid. E3. The method of embodiment 2, wherein the clay comprises a material selected from a group consisting of montmorillonite, smectite, heulandite, mordenite and combinations thereof. E4. The method of embodiments 2 or 3, wherein the clay is comprised in a tank, bed or column. E5. The method of embodiments 2-4, wherein the clay removes aqueous components from the organic solution to a concentration of about 3000 ppm or less of the aqueous components. E6. The method of any of the preceding embodiments, further comprising: settling the organic solution in a tank until an organic phase separates from an aqueous phase; and removing the aqueous phase. E7. The method of any of the preceding embodiments, further comprising: coalescing the organic solution with a coalescer or an electrostatic coalescer to separate an organic phase from an aqueous phase; and removing the aqueous phase. E8. The method of any of the preceding embodiments, wherein the polar solid is comprised in a low-pressure column or a pressure column. E9. The method of any of the preceding embodiments, wherein the organic solution is partially loaded with the non-polar complexes. E10. The method of embodiments 1-8, wherein the organic solution is fully loaded with the non-polar complexes. E11. The method of any of the preceding embodiments, wherein the organic solution comprises a water immiscible solvent and a reagent selected from a group consisting of a ketoxime, an aldoxime and combinations thereof. E12. The method of any of the preceding embodiments, wherein the water immiscible solvent is selected from a group consisting of kerosene, benzene, toluene, xylene and combinations thereof. E13. The method of any of the preceding embodiments, wherein the organic solution comprises a phenolic oxime. E14. The method of any of the preceding embodiments, wherein the organic solution comprises a phenolic oxime in the organic solution is about 0.018 M to about 1.1 M. E15. The method of any of the preceding embodiments, wherein the organic solution comprises a ketoxime or an aldoxime at a concentration of about 0.018 M to about 0.9 M. E16. The method of any of the preceding embodiments, wherein the organic solution comprises a modified or non-modified phenolic oxime. E17. The method of any of the preceding embodiments, wherein the organic solution comprises 3-methyl ketoxime, 3-methyl aldoxime, 2-hydroxy-5-nonylacetophenone, 5-nonylsalicylaldoxime, 5-dodecylsalicylaldoxime, or combinations thereof. E18. The method of any of the preceding embodiments, wherein the organic solution comprises a 3-methyl ketoxime and a 3-methyl aldoxime in a molar ratio of about 85:15 to about 25:75. E19. The method of any of the preceding embodiments, wherein the non-polar complexes comprise a metal selected from a group consisting of copper, iron, nickel, zinc, metal alloys thereof and combinations thereof. E20. The method of any of the preceding embodiments, wherein the organic solution comprises polar compounds comprising phenolic oxime compounds and oxime hydrolysis byproducts. E21. The method of any of the preceding embodiments, wherein the organic solution comprises oxime hydrolysis byproducts comprising ketone compounds, aldehyde compounds or combinations thereof. E22. The method of any of the preceding embodiments, further comprising receiving the organic solution from a solvent extraction process. E23. The method of any of the preceding embodiments, wherein the polar solid comprises a material selected from the group consisting of silica, alumina, activated carbon and combinations thereof. E24. The method of any of the preceding embodiments, wherein the polar solid comprises silica. E25. The method of any of the preceding embodiments, further comprising: regenerating the polar solid to remove adsorbed polar compounds by contacting the polar solid with a polar solvent.

Following are more embodiments of the invention.

E1. A method of recovering metal from a metal-containing aqueous solution, comprising: contacting an aqueous solution comprising a metal with an organic solution to extract a portion of the metal into the organic solution and forming a metal-loaded organic solution comprising polar compounds and a metal-depleted aqueous solution; separating the metal-loaded organic solution from the metal-depleted aqueous solution; removing a portion of the polar compounds from the metal-loaded organic solution by contacting the metal-loaded organic solution with a polar solid to adsorb the polar compounds onto the polar solid and forming a treated metal organic solution; recovering metal values from the treated metal organic solution. E2. The method of embodiment 1, wherein removing further comprises: contacting the metal-loaded organic solution with a clay prior to the contacting with the polar solid. E3. The method of embodiment 2, wherein the clay comprises a material selected from a group consisting of montmorillonite, smectite, heulandite, mordenite and combinations thereof. E4. The method of embodiments 2 or 3, wherein the clay is comprised in a tank, bed or column. E5. The method of embodiments 2-4, wherein the clay removes aqueous components from the organic solution to a concentration of about 3000 ppm or less of the aqueous components. E6. The method of any of the preceding embodiments, further comprising: receiving the aqueous solution from a process selected from a group consisting of heap leaching, hydrometallurgical leaching, high pressure leaching, oxidative leaching, biologically assisted leaching and combinations thereof. E7. The method of any of the preceding embodiments, wherein the aqueous solution is at a temperature of about 20° C. to about 60° C. E8. The method of any of the preceding embodiments, wherein the metal values are selected from a group consisting of copper, iron, nickel, zinc, metal alloys thereof and combinations thereof. E9. The method of any of the preceding embodiments, wherein the organic solution comprises a water immiscible solvent and a reagent selected from a group consisting of a ketoxime, an aldoxime and combinations thereof. E10. The method of any of the preceding embodiments, wherein the water immiscible solvent is selected from a group consisting of kerosene, benzene, toluene, xylene and combinations thereof. E11. The method of any of the preceding embodiments, wherein the organic solution comprises a phenolic oxime. E12. The method of any of the preceding embodiments, where the organic solution comprises a phenolic oxime at a concentration from about 0.018 M to about 1.1 M. E13. The method of any of the preceding embodiments, wherein the organic solution comprises a phenolic ketoxime or an aldoxime at a concentration of about 0.018 M to about 0.9 M. E14. The method of any of the preceding embodiments, wherein the organic solution comprises a phenolic oxime which is modified or non-modified. E15. The method of any of the preceding embodiments, wherein the organic solution comprises 3-methyl ketoxime, 3-methyl aldoxime, 2-hydroxy-5-nonylacetophenone, 5-nonylsalicylaldoxime, 5-dodecylsalicylaldoxime, or combinations thereof. E16. The method of any of the preceding embodiments, wherein the organic solution comprises a 3-methyl ketoxime and a 3-methyl aldoxime in a molar ratio of about 85:15 to about 25:75. E17. The method of any of the preceding embodiments, wherein the polar compounds comprise phenolic oximes and oxime hydrolysis byproducts. E18. The method of any of the preceding embodiments, where the polar compounds comprise oxime hydrolysis byproducts comprising ketone compounds, aldehyde compounds and combinations thereof. E19. The method of any of the preceding embodiments, wherein contacting the aqueous solution with the organic solution and separating the metal-loaded organic solution from the metal-depleted aqueous solution comprises a solvent extraction process. E20. The method of any of the preceding embodiments, wherein removing a portion of the polar compounds from the metal-loaded organic solution comprises passing a bleed stream from a main stream of the metal-loaded organic solution through the polar solid and passing the treated metal organic solution to the main stream. E21. The method of any of the preceding embodiments, further comprising: measuring one or more parameters of the metal-loaded organic solution and of the treated metal organic solution and adjusting a flow rate through the polar solid based on the measured parameter. E22. The method of embodiment 21, wherein the one or more parameters are indicative of an amount of polar compounds in the metal-loaded organic solution and the treated metal organic solution. E23. The method of embodiments 21 or 22, wherein the one or more parameter is selected from a group consisting of conductivity, viscosity, density, pH, temperature, pressure and combinations thereof. E24. The method of embodiments 21-23, wherein adjusting the flow rate based on the one or more parameter comprises adjusting the flow rate to achieve at least one of a target conductivity and target viscosity of the treated metal organic solution. E25. The method of embodiments 21-24, further comprising measuring the one or more parameter of the aqueous solution. E26. The method of any of the preceding embodiments, wherein the polar solid is comprised in a low-pressure column or a pressure column. E27. The method of any of the preceding embodiments, wherein the polar solid comprises a material selected from a group consisting of silica, alumina, activated carbon and combinations thereof. E28. The method of any of the preceding embodiments, wherein the polar solid comprises silica. E29. The method of any of the preceding embodiments, further comprising: regenerating the polar solid to remove adsorbed polar compounds by contacting the polar solid with a polar solvent.

EXAMPLES Example 1—Silica Gel Loading at Varying Amounts by Batch Test

A synthetic organic solution of about 0.15 mol/L (M) C₉ ketoxime (Ket) and 0.18 M C₉ aldoxime (Ald) was prepared and used for all three experiments. In addition about 0.2 M C₉ ketone (HNA) and about 0.2 M C₉ aldehyde (NSA), the respective hydrolysis products, were added to simulate degradation. The solution was made up in a 2×2 L volumetric flasks and diluted in Shellsol D-70 kerosene diluent. The total 4 liters was mixed together. 800 ml of the solution was removed and set aside while the rest of the solution was max loaded with copper according to standard BASF quality control procedures. This was done by contacting the organic with 20 g/L Cu aqueous, pH about 4, 4 times at an organic: aqueous volume ratio of 1. The organic was separated from the aqueous by gravity separation in a 2 L sep-funnel. Once the organic solution was max loaded, the 800 ml aliquot was added back into the solution and mixed. This left an organic solution of oxime and hydrolysis products that was loaded to approximately 80% of max load (ML). This solution roughly models that of loaded-organic found in highly degraded SX circuits found around the world. This solution as described will be referred to as “fresh organic” in the following experiments.

In this experiment six contacts were made between fresh organic and fresh silica gel. This experiment examined the batch mixing of the two in different ratios from 1% silica gel to 40% silica gel (1% silica gel=1 g silica gel/100 ml organic). Fresh organic (100 ml) was mixed with 1-40% silica gel (silica gel 230-400 mesh, Fisher) for 1 min in a baffled beaker at 800 RPM. The silica gel was then filtered out by gravity filtration and washed with 100 ml of kerosene diluent. A sample of the filtered organic was analyzed for components. The recovered and washed silica gel was eluted with 50:50 hexane:ethylacetate (by volume). The eluent was dried, weighed, and analyzed by gas chromatography (GC) for relative amounts of components. Results are found in Table 1.1 and FIGS. 1.1 and 1.2.

TABLE 1.1 Tabulated data for Example 1 Cu (M) Bulk Organic Composition (M) ML As is Org. % ML Recovered from SiO2 (g) SiO2 (g) Ald NSA Ket HNA NP Start Org 0.1778 0.1324 74.4% 0.4370 0.2072 0.3601 0.1923 0.1101  1% SiO2 0.1712 0.1322 77.2% 0.1379 0.8341 0.4252 0.2201 0.3417 0.2010 0.1101  5% SiO2 0.1684 0.1363 80.9% 0.7351 4.8482 0.4218 0.1931 0.3320 0.1896 0.0931 10% SiO2 0.1646 0.1366 83.0% 1.4500 9.7553 0.4165 0.1910 0.3198 0.1789 0.0765 15% SiO2 0.1605 0.1445 90.0% 2.4291 14.5230 0.4131 0.1753 0.3043 0.1667 0.0663 25% SiO2 0.1632 0.1412 86.5% 3.8176 25.1234 0.4268 0.1733 0.3014 0.1457 0.0464 40% SiO2 0.1454 0.1399 96.2% 5.7616 35.6650 0.3846 0.1391 0.2639 0.1110 0.0268

FIG. 4.1 shows that increased amounts of hydrolysis products are removed from the organic, with increased amounts of silica gel. However FIG. 4.2 shows a loss of oxime with 40% silica gel that may suggest the slight loss of components other than unloaded oxime. Also referring to Table 1.1 above, it can be seen that there is a significant removal of nonyl phenol (NP) from the organic (about 76% loss). NP is a starting material for the production of phenolic oximes and is found in not only the formulated product, but also in SX circuits around the world (on the order or 0.02-0.13 M).

Example 2—Multiple Silica Gel Contacts by Batch Test

In this experiment an organic solution (from Example 1) was progressively contacted with 5% w/v silica gel over nine (9) contacts (5% w/v silica gel calculated as 1% w/v silica gel=1 g silica gel/100 ml organic). This experiment was meant to examine the effects of progressive removal of components from the organic in a batch type process. Fresh organic (500 ml) was contacted with 25 g of silica gel (5% w/v silica gel) for 1 min in a baffled beaker at 800 RPM. This organic was then vacuum filtered to separate out the silica gel. The organic was then contacted again with fresh 5% w/v silica gel and filtered again (organic volume was reduced due to loss in filtering after each contact, thus the amount of silica gel was adjusted accordingly to maintain 5% w/v). This was done a total of nine (9) times. After each contact a sample of organic was collected and analyzed for components. After each filtering, the recovered silica gel was washed with 100 ml of kerosene diluent and stripped with 50:50 hexane:ethylacetate. The stripped material was dried, weighed, and analyzed by GC for relative amounts of components. Results are found in Table 2.1 and FIGS. 5.1 and 5.2.

TABLE 2.1 Tabulated data for Experiment 2 Start org vol. Cu (M) Bulk Organic Composition (M) Contact (ml) SiO2 (g) ML Ald NSA Ket HNA NP 0 0 0.1778 0.4370 0.2072 0.3601 0.1923 0.1101 1 500 25.00 #VALUE! #VALUE! 0.2434 #VALUE! 0.2018 0.1025 2 450 22.50 0.1584 0.3994 0.2084 0.3093 0.1820 0.0833 3 425 21.25 0.1542 0.3960 0.1943 0.2931 0.1667 0.0663 4 385 19.25 0.1524 0.3937 0.1640 0.2866 0.1553 0.0540 5 350 17.50 0.1332 0.3493 0.1580 0.2455 0.1392 0.0434 6 325 16.25 0.1458 0.3842 0.1552 0.2657 0.1297 0.0327 7 290 14.50 0.1424 0.3808 0.1491 0.2538 0.1202 0.0285 8 265 13.25 0.1426 0.3789 0.1362 0.2567 0.1072 0.0217 9 245 12.25 0.1374 0.3698 0.1201 0.2419 0.0938 0.0166

As in Example 1, it can be seen that hydrolysis products are removed (about 50%). Oxime is removed to roughly the same degree as in Example 1 (about 30% loss of ketoxime to remove about 50% hydrolysis product). Note the drop in contact #5 in FIG. 5.2 is most likely due to a compromised sample). The loss of NP is also large (85%).

Example 3—Varying Polar Solid Flash Columns

Three polar solids were tested in a flash column to test removal of impurities. Silica gel, activated carbon and activated clay were tested. Each one of the tests was conducted in the same manner only varying the amount and type of solid. The following solids were used: F1 clay (BASF), silica gel 230-400 mesh (Fisher), and a 1:19 mixture of activated carbon powder (J. T. Baker) and coarse granules (Draco GD12X30).

A flash column was set up using pressure glassware. A pressure manifold was made using a valve, an adjustable pressure relief valve and a pressure gauge. A 250 mL pressure equalizing addition funnel was attached to a small column with about 30 mL volume. The manifold was attached to the compressed air source then to the top of the flash column assembly using flexible tubing. The entire assembly was supported in a hood and the column ran pressurized at 5 psi.

The column was packed with glass wool, a weighed amount of polar solid and glass wool. The organic used was 0.075 mol/L (M) C₉ ketoxime (Ket) and 0.09 M C₉ aldoxime (Ald) in Shellsol D70 max loaded with copper according to standard BASF quality control procedures. The organic was spiked with 0.1 M C₉ ketone (HNA) and 0.1 M C₉ aldehyde (NSA). Each test passed 500 ml of the organic through the column collecting fractions at approximately 100 mL. After the column had run dry and the solution had stopped dripping out of the column 100 mL of hexane was passed through the column. When the hexane stopped dripping out of the column 100 ml of acetone was passed through the column. The acetone fraction was dried to remove the solvent and the residue was diluted to 50 ml in toluene. Each fraction, hexane wash, and toluene residue was stripped with 250 g/L acid (two 1:1 contacts with acid followed by a 1:1 contact with deionized water). These stripped samples were analyzed by GC using standards for determination of NP, HNA and NSA. The remaining unstripped samples, hexane wash and toluene residue were analyzed by atomic absorption spectroscopy (AA) for copper.

The diluent passed through the column much faster than the other species, allowing collection of a 75 mL first fraction of clear diluent. After this, four more fractions were taken every hour. After the all of the solution had passed through the column and it was run dry, 100 mL of hexane were passed through the column to remove any trapped oxime that was not bound to the column, this took only one or two column volumes to remove the majority of the oxime. 100 mL of acetone was passed through the column to strip a majority of the remaining impurities. The results of these column trials indicate that silica gel is the most effective at removing hydrolysis products, followed by the clay column and the carbon column. Results are found in Tables 3.1, 3.2 and 3.3.

TABLE 3.1 Silica gel Column Results 500 ml of Organic and 24.9912 g Silica Gel Fraction ML (g/L Cu) NP (M) HNA (M) NSA (M) Starting Organic 5.428 0.033 0.024 0.031 1 0 0.000 0.000 0.000 2 6.301 0.001 0.007 0.003 3 6.474 0.002 0.014 0.039 4 6.042 0.001 0.030 0.032 5 5.905 0.001 0.033 0.030 Hexane 2.368 0.001 0.025 0.026 Acetone 0.724 0.285 0.036 0.036

TABLE 3.2 Clay Column Results 250 ml of Organic and 5.0132 g Clay Fraction ML (g/L Cu) NP (M) HNA (M) NSA (M) Starting Organic 5.428 0.033 0.024 0.031 1 5.031 0.01 0.01 0.02 2 5.436 0.03 0.02 0.03 3 5.356 0.03 0.02 0.03 4 5.351 0.03 0.02 0.03 Hexane 0.2929 0.01 0.00 0.00 Acetone 0.083 0.01 0.00 0.00

TABLE 3.3 Carbon Column Results 500 ml of Organic with 20.00 g Carbon Mixture Fraction ML (g/L Cu) NP (M) HNA (M) NSA (M) Starting Organic 5.428 0.033 0.024 0.031 1 4.523 0.018 0.016 0.022 2 5.168 0.027 0.016 0.023 3 5.256 0.029 0.017 0.024 4 5.286 0.029 0.019 0.026 5 5.246 0.030 0.016 0.025 Hexane 0.515 0.008 0.003 0.005 Acetone 0.438 0.026 0.003 0.005

Example 4—Silica Gel Re-Use

The purpose of this experiment was to test the effectiveness of stripping the silica gel and any subsequent reduction in the silica gel's loading capacity. This experiment followed Example 2 exactly, using the same method and starting organic. This time the organic was re-passed through the same silica gel column after stripping the column without replacing the silica gel. This was repeated so that the organic was passed through the column for a total of three times. After stripping the column, using the same silica gel, a fresh batch of organic was passed through the column, the same batch of organic was used up, so for this pass a new batch of organic was made up which had very similar levels of degradation. Results are found in Table 4.1 and FIGS. 6.1, 6.2 and 6.3.

TABLE 4.1 Summary of Example 4 results Sample ML (g/L Cu) NP (M) HNA (M) NSA (M) Starting organic (1st pass) 5.428 0.033 0.024 0.031 Starting organic (2nd 5.255 0.031 0.025 0.028 organic) 1st Pass 5.23 0.002 0.019 0.023 2nd Pass 4.531 0.001 0.013 0.017 3rd Pass 4.362 0.000 0.013 0.017 2nd organic 5.02 0.002 0.023 0.026 1st Hexane 1.826 0.001 0.028 0.030 2nd Hexane 3.168 0.002 0.020 0.027 3rd Hexane 0.793 0.000 0.006 0.007 4th Hexane 1.028 0.003 0.027 0.025 1st Acetone 0.667 0.287 0.034 0.025 2nd Acetone 0.1719 0.001 0.032 0.023 3rd Acetone 0.018 0.000 0.000 0.000 4th Acetone 0.088 0.275 0.008 0.015

It can be seen that as the same org passes through, progressively smaller amounts of the hydrolysis products are removed by comparison of the first, second and third passes of the same organic. When a second, fresh organic is passed through a regenerated silica column, the data demonstrates a reduced efficacy of the column by comparison of the first pass to the second organic pass.

Example 5—Silica Gel Loading Capacity in a Flash Column

A flash column was set up and loaded with 10 g of silica gel. Then fresh organic (500 ml) was passed through the column. The silica gel was subsequently replaced with another 10 g of silica gel and the same organic was passed through the column again. This was repeated for eight passes through the column with fresh silica gel but the same 500 ml of organic each time. Samples of the organic were taken after each pass and analyzed by GC. Results are found in FIG. 7.1.

Example 6—Silica Gel Large Column Comparison

Fresh organic (500 ml) was passed over 40.0 g of silica gel through a larger column, otherwise following Example 4. No strip using hexane or acetone was performed. Included in the results is the fourth pass organic from Example 5 to show a comparison of an organic being passed over four 10 g portions of silica gel and one 40 g portion. The removal of copper and NP were identical, the removal of NSA was slightly better for the one large column and removal of HNA was substantially better in the large column. Results are found in FIG. 8.1.

Example 7—Alumina Use as a Polar Solid

Two more columns were run using 25.0 g of alumina, aluminum oxide activated basic (Alfa Aesar) and alumina oxide activated (Spectrum). These followed exactly Example 4 with the use of alumina. The flow rates of these columns were much faster than that of the silica gel columns, passing the 500 ml in less than one hour. It was also noted that the alumina was stained green (similar to the color of dilute ketoxime) even after the acetone strip. Results are found in FIGS. 9.1, 9.2 and 9.3.

The results include the silica gel results from Example 3 for comparison. It can be seen that using the same weights of activated (heat) alumina and basic alumina that both behaved similarly. Basic alumina removed slightly more HNA and NSA, but less NP in the organic. The activated alumina passed more degrandants into the hexane especially NP. The acetone wash was similar for both. Silica gel removed the degradants at a much higher rate specifically with NP which was removed at a higher concentration and stripped with the acetone.

Example 8—Degradation Removal Using Varying Polar Solids

In this set of tests, the main focus was on the use of silica gel, but carbon, activated clay, and activated alumina all removed degradants. Using the results of each column the capacity of each polar solid can be determined. It is important to note that there may be many factors that impact loading of degradants on the columns: amount of each degradant in the organic being treated, competition of other degradants in solution, size of column, and amount of time the organic is in contact with the polar solid. To best summarize these results two sets of results will be examined, first, the 25 g columns that were contacted with fresh 500 ml of organic and second, the eight passes of the same organic through fresh 10 g silica gel columns. The first shows the capacity of each polar solid for any degradant, ignoring competition of the three degradants. The second shows how the capacity of the polar solid changes as the degradants are removed.

Each column using various polar solids can be compared by looking at how much degradant is removed from each organic based on the starting weight of each degradant in the 500 ml portion put through the column and how much remains in the organic after being passed through the column. From this, a total weigh of degradants removed can be calculated and then the capacity of the polar solid can be determined. Each column used 25 g except for the clay column which did not allow the solution to be passed through the column at 25 g. About 5 g of silica gel and 250 ml of organic was used. See Table 8.1 for these results.

TABLE 8.1 Summary of Each Organic After Passing Through Various Polar Solids Grams Media (per Grams removed 500 ml g removed/ Media reagent) HNA NSA NP HNA NSA NP total g solid Start None 3.091 3.889 3.851 Silica 25 2.892 2.589 0.128 0.199 1.3 3.723 5.222 0.209 Clay 10 2.079 2.798 2.945 1.012 1.091 0.906 3.009 0.301 Carbon 25 2.079 2.798 2.945 1.012 1.091 0.906 3.009 0.120 Alumina 25 2.37 3.288 2.723 0.721 0.601 1.128 2.45 0.098 Basic 25 1.972 3.139 3.139 1.119 0.75 0.712 2.581 0.103 Alumina

These results indicate that the clay is very effective in removing degradants; however, it must be considered that some of these degradants are recovered in the wash step or are permanently bound to the polar solid. Therefore, two other factors should be considered: how much is removed by the acetone strip and how much is stained on the polar solid. The grams of lost degradants is calculated as the sum of degradants in the starting organic minus the sum of degradants in the organic, hexane and acetone.

TABLE 8.2 Summary of Each Hexane Wash of Various Polar Solids Hexane Grams Grams removed Media (per g 500 ml released/ Media reagent) HNA NSA NP total g solid Silica 25 0.625 0.614 0.026 1.265 0.051 Clay 10 0.062 0.081 0.16 0.303 0.030 Carbon 25 0.09 0.121 0.18 0.391 0.016 Alumina 25 0.089 0.151 0.417 0.657 0.026 Basic Alumina 25 0.078 0.105 0.162 0.345 0.014

TABLE 8.3 Summary of Each Acetone Wash of Various Polar Solids and Calculation of Lost Degradants Acetone Grams Media Grams removed (per g 500 ml recovered/ g lost/g Media reagent) HNA NSA NP total g solid solid Silica 25 0.467 0.44 3.347 4.254 0.170 0.21248 Clay 10 0.011 0.016 0.072 0.099 0.010 1.0429 Carbon 25 0.037 0.059 0.304 0.400 0.016 0.4016 Alumina 25 0.017 0.092 1.171 1.280 0.051 0.35576 Basic 25 0.082 0.166 0.861 1.109 0.044 0.37508 Alumina

It can be seen from Tables 8.2 and 8.3 that silica gel has by far the highest ability to load degradants and then be stripped by acetone. Additionally, silica gel had the lowest amount of lost degradants.

The results of this experiment show the need for the reagent to be max loaded before passing through a polar solid and the need for a rinse of the polar solid before stripping the solid. The comparison of this can be seen in the examples that used 20% v/v LIX984N loaded to 80% of its maximum loading as compared to those that used 10 v/v % LIX984N loaded to 100% of its maximum loading (atmospheric pressure vs. 5 psi).

TABLE 8.4 Comparison of Reagent Loss from the Examples Experiment 3.1 3.8 1st Starting Cu g/L 11.3 5.428 Recovered Cu g/L 10.37 5.23 Wash Cu g/L 1.826 Reagent:Wash ratio 10 % Oxime Lost with out Wash 8.2% 3.6% % Oxime Lost with Wash 0.3%

Table 8.4 shows that the oxime loss was 8.2% when the reagent was loaded only 80% of the max load. The losses drop to 3.6% when the reagent is loaded completely. When a wash of the silica gel was used before stripping only 0.3% of the oxime was lost.

It is to be understood that the phraseology or terminology used herein is for the purpose of description and not of restriction, such that the terminology or phraseology of the present specification may be interpreted by those of ordinary in the art in light of the teachings and guidance presented herein, in combination with the knowledge of those of ordinary skill in the relevant art(s).

The various aspects disclosed herein encompass present and future known equivalents to the known components referred to herein by way of illustration. Furthermore, while aspects and applications have been shown and described, it will be apparent to those of ordinary skill in the art having the benefit of this disclosure that many more modifications than mentioned above are possible without departing from the inventive concepts disclosed herein. 

1. A method of recovering metal from a metal-containing aqueous solution, comprising contacting an aqueous solution comprising a metal with an organic solution to extract a portion of the metal into the organic solution and forming a metal-loaded organic solution comprising polar compounds and a metal-depleted aqueous solution; separating the metal-loaded organic solution from the metal-depleted aqueous solution; removing a portion of the polar compounds from the metal-loaded organic solution by contacting the metal-loaded organic solution with a polar solid to adsorb the polar compounds onto the polar solid and forming a treated metal organic solution; and recovering metal values from the treated metal organic solution.
 2. The method of claim 1, wherein removing further comprises contacting the metal-loaded organic solution with a clay prior to the contacting with the polar solid.
 3. The method of claim 1, wherein the metal values are selected from a group consisting of copper, iron, nickel, zinc, metal alloys thereof and combinations thereof.
 4. The method of claim 1, wherein the organic solution comprises a water immiscible solvent and a reagent selected from a group consisting of a ketoxime, an aldoxime and combinations thereof.
 5. The method of claim 1, wherein the water immiscible solvent is selected from a group consisting of kerosene, benzene, toluene, xylene and combinations thereof.
 6. The method of any of claims 1 to 5, wherein the organic solution comprises a phenolic oxime.
 7. The method of claim 6, wherein a concentration of the phenolic oxime in the organic solution is about 0.018 M to about 1.1 M.
 8. The method of claim 6, wherein the phenolic oxime is a ketoxime or an aldoxime at a concentration of about 0.018 M to about 0.9 M.
 9. The method of any of claims 1 to 5, wherein the organic solution comprises 3-methyl ketoxime, 3-methyl aldoxime, 2-hydroxy-5-nonylacetophenone, 5-nonylsalicylaldoxime, 5-dodecylsalicylaldoxime, or a combinations thereof.
 10. The method of any of claims 1 to 5, wherein the organic solution comprises a 3-methyl ketoxime and a 3-methyl aldoxime in a molar ratio of about 85:15 to about 25:75.
 11. The method of any of claims 1 to 5, wherein the polar compounds comprise phenolic oximes and oxime hydrolysis byproducts.
 12. The method of claim 11, wherein the oxime hydrolysis byproducts comprise ketone compounds, aldehyde compounds and combinations thereof.
 13. The method of any of claims 1 to 5, wherein contacting the aqueous solution with the organic solution and separating the metal-loaded organic solution from the metal-depleted aqueous solution is via a solvent extraction process.
 14. The method of any of claims 1 to 5, wherein removing a portion of the polar compounds from the metal-loaded organic solution comprises, passing a bleed stream from a main stream of the metal-loaded organic solution through the polar solid and passing the treated metal organic solution to the main stream.
 15. The method of claim 1 or 13, further comprising measuring one or more parameter of the metal-loaded organic solution and of the treated metal organic solution and adjusting a flow rate through the polar solid based on the measured parameter.
 16. The method of any of claims 1 to 5, wherein the polar solid is comprised in a low-pressure column or a pressure column.
 17. The method of any of claims 1 to 5, wherein the polar solid comprises a material selected from a group consisting of silica, alumina, activated carbon and combinations thereof.
 18. The method of any of claims 1 to 5, wherein the polar solid comprises silica.
 19. The method of any of claims 1 to 5, further comprising regenerating the polar solid to remove adsorbed polar compounds by contacting the polar solid with a polar solvent.
 20. A method for removing polar compounds from a solution, comprising contacting an organic solution comprising non-polar metal complexes and polar compounds with a polar solid and adsorbing the polar compounds onto the polar solid. 